TEMPERATURE EFFECTS ON THE BIOCHEMICAL COMPOSITION OF MICROBES AND PLANKTON

It is unclear how global warming will affect aquatic biogeochemical processes and food webs. We examined some aspects of these issues in a chemostat with Escherichia coli and with field-collected samples. In the chemostat as well as the field-collected samples, the P content of organisms decreased with increasing temperature. Both in marine and freshwater systems, there was a pronounced decrease in the seston C:P ratio with depth in summer. Decreased RNA, which is relatively P-rich (10% by weight), accounted for most of the decreased P content at high temperatures in chemostats. Although it has been argued that currently increased N:P ratios in the World Ocean are a consequence of increased nitrogen deposition, we argue that increased temperatures may also be important. Our results suggest that production at low temperatures may be more nutritious to consumers than production at high temperatures and suggests that carbon burial efficiencies may increase at high temperatures.